Embodiments of the present invention generally relate to methods for depositing metals. Specific embodiments of the invention are directed to methods for the deposition of tantalum nitride (TaN) using CVD or ALD techniques.
Atomic Layer Deposition (ALD) deposited tantalum nitride (TaN) is a promising candidate for copper barrier, especially for very fine structures. The deposition of TaN as a copper barrier can be performed on bare substrates or various underlayers, including, but not limited to low-k dielectrics. Tantalum nitride films are used, for example, in front end of line (FEOL) processes as an etch stop on top of a work function material to protect gate materials and as a barrier for aluminum deposition. TaN is also used in back end of line (BEOL) processes as a copper barrier to prevent diffusion of copper into the adjacent layer.
Generally, a larger amount of tantalum results in better adhesion of a subsequently deposited layer. In processing TaN, higher power plasma is known to damage the TaN layer. Such damage can include, higher capacitances, increase dielectric constant resulting in greater leakage currents, etching of carbon in low-k films, collapsing of the pores in low-k films and penetration through high-k films and interface layer. Damage to the underlying layers is a concern in processes that include, but are not limited to, metal gate deposition, formation of a treatment film on a low K films, and silicide deposition. In metal gate deposition, the substrate may be Si and may include a thin oxide layer deposited on the Si substrate having a thickness of less than about 10 Å, a high K oxide disposed on the thin oxide layer having a thickness less than about 20 Å, an optional cap layer having a thickness in the range from about 10 Å to about 20 Å and a metal gate layer such as a tantalum or cobalt metal layer. In processes for providing a treatment film on a low K film, the substrate includes a low K material, a barrier layer deposited on the substrate followed by a metal deposition on the barrier layer or treatment of the barrier layer. The barrier layer in such processes is typically thin. In silicide deposition, the substrate typically includes Si and includes a metal silicide layer disposed thereon and cleaned and a barrier layer is disposed on the metal silicide layer.
There is an ongoing need to develop methods of depositing TaN films having one or more of better performance, higher film density, lower resistivity, less or no plasma damage and uniform barrier coverage and stop coverages.